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How much will he spend and borrow?

"I've spent my entire life in business looking at the untapped potential in projects and people around the world. That is what I now want to do for our country," said Mr Trump as he set out his stall when the results came in.

"We're going to rebuild our infrastructure, which will become second to none. We will put millions of our people to work as we rebuild it."

He has previously complained that the country's bridges are in a poor state, as well as pledging to spend more on roads and airports.

To finance that, Mr Trump has indicated he would spend "at least double" Hillary Clinton's proposed $275bn (£221bn) on infrastructure, indicating more than $500bn, as well as proposing $137bn in tax credits for private firms willing to spend on construction. He has also referred to his proposals as a "trillion-dollar rebuilding plan" without backing up where the rest of the money will come from.

At the same time he has also promised a wave of tax cuts, chopping the Federal corporation tax rate by more than half from 35pc to 15pc, as well as simplifying income tax which he said is "a tax cut for all income groups".

The incoming President has also backed a major defence spending splurge.

In very simple terms, a government spending spree provides a short-term boost to the economy. But unsustainable borrowing can also store up trouble for the government and the wider economy further down the line, particularly when the country relies on foreign investors to fund its debts.

"We should remember that the US bond market is heavily owned by foreigners, including nations like China where Trump has made unfriendly comments," said Jim Leaviss, head of retail fixed interest at M&G Investments.

"50pc of the US Treasury market is owned by overseas investors (China owns 19pc, Japan 18pc), and 30pc of America's corporate bond market is foreign owned."

What does that mean for the deficit?

The Republican Party has fiercely opposed big rises in borrowing in recent years, objecting to President Obama's plan to raise the debt ceiling which led to a debt crisis in 2011.

Mr Trump's plans appear to amount to a substantial fiscal stimulus, however, which would push up borrowing rapidly and could mean the debt ceiling needs to be raised once more - potentially provoking a row with the Republican-dominated congress and senate, many members of which previously opposed more borrowing.

"We doubled the debt over the last eight-year period and the worst part about the doubling of the debt, we have not got anything with it - we have not rebuilt bridges or highways or roads or airports," he told CNBC in September.

"The whole thing is a mess. We are $20 trillion [in debt] and our infrastructure is a disaster."

The Committee for a Responsible Federal Budget estimates that Mr Trump's plans would add $5.3 trillion to the US national debt.

"The much looser fiscal policy will not make it any easier for the US government to balance its budget, with the upcoming debt ceiling debate, in March 2017, which will become even more a recurring topic of conversation in Washington," said Dierk Brandenburg, senior sovereign analyst, Fidelity International.

"As an initial estimate, the proposed fiscal stimulus will lead to a doubling of outstanding federal debt in the next decade and to a dramatic widening of the US primary deficit."

It could prove tough for Mr Trump to finance that borrowing - although the US dollar is the world's reserve currency, which boost demand for dollar-denominated assets, he could strain this to the limits.

What will his Presidency mean for the Fed?

Central banks have rarely been more core to the world economy and to stock markets in particular, with the Federal Reserve holding substantial power over market sentiment.

The Fed was widely expected to raise interest rates next month as the economy strengthens and officials seek to move monetary policy off its emergency footing, which has continued since the financial crisis.

Before the vote, markets believed there was an 80pc chance of a hike in December. That dived to below 50pc immediately after the vote before bouncing back again to more than 70pc.

Traders work as Janet Yellen, chair of the U.S. Federal Reserve, is seen speaking on a television screen on the floor of the New York Stock Exchange. Photo / AP

Traders work as Janet Yellen, chair of the U.S. Federal Reserve, is seen speaking on a television screen on the floor of the New York Stock Exchange. Photo / AP

That indicates wild uncertainty in markets over the Fed's actions - it could seek to reassure investors by offering sustained easy money, for example, or keep rates low to bolster economic growth in the coming years.

Alternatively, the new President's spending plans could prove highly inflationary - particularly if he chokes off the supply of workers from abroad, pushing up wage inflation - forcing more rate hikes over time.

"The US economy is now close to full employment and, as the latest figures suggest, wage inflation is beginning to accelerate," said Larry Hatheway, chief economist at GAM.

"US fiscal expansion is therefore likely to elicit a more rapid series of Fed rate hikes than would have been expected in a Clinton presidency."

And for Janet Yellen?

The longer-term future of the Fed is also far from clear, as Mr Trump has been critical of the central bank and its chair, Janet Yellen.

Her four-year term expires in February 2018, barely one year into the Trump Presidency.

In September, Mr Trump complained that Ms Yellen held rates "artificially low", repeating claims he made in 2015 that the Fed was acting politically to support Barack Obama.

But in March he said "I happen to be a low-interest-rate person", apparently supporting the policy, and he has also said "I have great respect for her".

On other occasions he said "I would imagine that we would put a Republican in that position", as well as noting that he believes the job is open to political influence.

"It is obviously not even close to being independent," he told CNBC in September, again indicating he would replace Ms Yellen.

The President-elect told the same interviewer that low interest rates are harmful for savers, but also that raising rates could trash the stock market.

"Even though Ms Yellen's term doesn't expire until February 2018, it is a reasonable guess is that she will resign already on January 20, 2017," said economist Mattias Bruér at the bank SEB.

"What many Republicans want is a rule-based approach to monetary policy which would suggest significantly higher fed funds rate compared to what we currently see. Since Republicans are on track to keep control of the House and are on the verge of retaining their majority in the US Senate, the likelihood of Trump's raw proposals have a much higher likelihood of becoming law."

What about immigration?

Perhaps Mr Trump's most famous pledge has been to build a wall along the US border with Mexico - paid for by a $5bn to $10bn contribution from Mexico, he has asserted - to reduce immigration.

The policy has sent the shares of cement and other construction-related firms through the roof this morning, though the actual construction plan and its timetable are less clear.

He has also indicated he wants to restrict migrations from specific religious groups, most notably Muslims.

It is part of wider plans to "establish new immigration controls to boost wages and to ensure that open jobs are offered to American workers first" and to place tighter restrictions on the type of workers allowed into the country.

Economists fear the idea could contribute to a shortage of labour, damaging economic growth and potentially driving up wages and prices.

"Trump has advocated selectively restricting immigration on the basis of religion and national origin. Whether the Congress will agree to such restrictions remains to be seen," said economist Kevin Logan at HSBC.

"However, Trump has indicated he will enforce current immigration laws to reduce the immigrant population through the deportation of undocumented immigrants. The number of illegal or undocumented immigrants may be close to 11m people. Deporting that many people would also lead to a sizable reduction in the country's labor force. That is turn could lead to a reduction in both actual and potential GDP growth."

What about trade with the wider world?

The euro also gained ground against the dollar in early Wednesday trading. Analysts at Citi believe that further increases in this direction will "strengthen the case for continued easing" by the European Central Bank. It still expects its asset purchase programme to be extended by 6 months to September 2017 - at a lower monthly pace of €60bn (from €80bn previously).

Mr Trump has helped to bring protectionist polices back into fashion.

Analysts at Investec believe the Transatlantic Trade and Investment Partnership (TTIP) trade deal between the US and EU and Trans-Pacific Partnership (TPP) deal between the US and 11 other Pacific Rim nations, including Japan, Australia and Peru is now "dead in the water".

This could start a new era of protectionism, according to economists at Citi. They said:

"US protectionism may divert emerging markets exports to the EU, strengthening protectionist forces in the EU as well, including at the Dutch and French elections in spring 2017. This could impact the upcoming Brexit negotiations: rising global protectionism limits the outside options for the UK and raises the values of strong ties with the EU."

While President Obama said that Britain would be "at the back of the queue" for a post-Brexit trade deal, Mr Trump extended a more friendly hand.

In an interview with ITV during the election campaign he said: "I don't want to say front [of the queue] or anything else - I would treat everybody fairly but it would not make any difference to me whether they were in the EU or not.

"You would certainly not be at the back of the queue, that I can tell you."

Any trade war with economic partners around the world would have a direct knock-on effect for the US economy, too: "There is a high risk of recession if the game ends in a trade war, depressing stock prices and treasury yields for a sustained period," said Rabobank analyst Bas van Geffen.

Other economies are also expected to cut interest rates or hike more slowly in response to the vote, in an effort to prop up growth: "With the euro appreciating, a further extension of European Central Bank quantitative easing at the next meeting in December looks increasingly inevitable while some kind of policy response from Bank of Japan and Swiss National Bank may also be forthcoming, possibly even foreign exchange intervention," said HSBC economist Janet Henry.

There are also implications for global security.

Citi continued: "Less forthcoming security support via NATO from the US could strengthen calls for a more potent EU security architecture, including higher defence spending. Less US support raises the uncertainty in particular at the Eastern borders of the EU."

The question now is whether his victory will influence upcoming elections in Europe, where discontent is growing.

Many say Marine Le Pen, the leader of the Front National, is on her way to the Élysée Palace next year.

Citi's Christian Schulz and Guillaume Menuet say this remains unlikely. They argue: "Investors may fear that National Front President Marine Le Pen could make it a hat trick of major political surprises in 2017 following the Brexit vote and Trump's victory.

In our view, one of the key differences in France is that Mrs Le Pen is well-established and almost 'mainstream‎'. She is not exactly a novelty in the French or European landscape and does not rank well with the majority of voters in terms of economic competency, even if she were to promise to 'make France great again'."

However, with December's Italian constitutional referendum proving the next major political test, followed by the Dutch and French elections in the spring and the German Federal elections in the autumn, Investec has a simple message: "Establishments beware."